Craters of the Moon

You're crossing the northern rim of the Snake River Plain, and what stretches across the horizon is one of the strangest landscapes in North America: a vast black ocean of frozen lava, cinder cones, and collapsed lava tubes, all of it looking very much like it cooled last Tuesday.

Craters of the Moon is the largest basaltic lava field in the contiguous United States. The eruptions here began roughly fifteen thousand years ago and the most recent flow is only about two thousand one hundred years old, a geological blink. The source is the Great Rift, a fifty-three-mile crack in the Earth's crust that slices across south-central Idaho, still seismically active and capable of erupting again. Geologists estimate the next eruption could come within the next thousand years.

President Calvin Coolidge made it a national monument in nineteen twenty-four, but the landscape got its most famous visitors in August of nineteen sixty-nine, just weeks after the first moon landing. NASA sent four Apollo astronauts here to study field geology: Alan Shepard, Edgar Mitchell, Joe Engle, and Eugene Cernan. They scrambled over the aa lava and pahoehoe flows, collected rock samples, and practiced identifying volcanic features before heading to a real lunar surface. The basalt at Craters of the Moon bears a striking chemical resemblance to samples brought back from the Moon, which is why NASA chose this place over any other volcanic field in the country.

The monument was expanded dramatically in two thousand, growing from eighty-three square miles to over eleven hundred square miles. It now absorbs the full extent of the lava field and adds grazing land, wilderness, and portions of the Snake River Plain Aquifer watershed.

The monument's name, suggested by an early explorer in the nineteen twenties, turned out to be accidentally prophetic: the astronauts who trained here walked on the actual Moon just weeks after leaving Idaho.